1. Field
Aspects of the example implementations pertain to the areas of thermoelectric devices and microfluidics, and more specifically to three-dimensional microfluidic micro-droplet arrays for electronic integrated circuit and component cooling, energy-harvesting, and other applications.
2. Overview
The cooling and energy harvesting of heat-producing integrated circuits and other electronic components in computers, particularly in large high-density blade servers and data center environments, is a topic both deserving of and gaining considerable importance to commerce. Technologies addressing these problems and opportunities can be found, for example, in pending U.S. patent application Ser. No. 13/385,411 and the references therein, including chapter 1 of the text Adaptive Cooling of Integrated Circuits Using Digital Microfludics by P. Paik, K. Chakrabarty, and V. Pamula, published by Artech House, Inc., Norwood, Me., Artech House, 2007, ISBN 978-1-59693-138-1.
The cooling of heat-producing integrated circuits in computers by means of controlled electrowetting micro-droplet transport via microfluidic device structures has been considered in considerable detail in the above-cited text by Paik, Chakrabarty, and Pamula. In Chapter 6 of that text, those authors describe approaches to implementing microfluidic device structures for controlled electrowetting micro-droplet transport for integrated circuit cooling using Printed Circuit Boards (“PCBs”).
In the afore-cited text, those authors describe first other approaches and general aspects of controlled electrowetting micro-droplet transport via microfluidic device structures. For example, FIG. 1a, adapted from the afore-cited text, depicts a side view representation of a microfluidic electrowetting micro-droplet transport “chip” implementation fitted over an integrated circuit package and in turn in thermal contact with an active cooling element such as a thermoelectric cooler. Additionally, FIG. 1b, adapted from the afore-cited text, depicts a top view representation of a number of micro-droplets being transported (via electrowetted transport) through various straight and right-angle-turn paths over a planar array of microelectrodes comprised by such a microfluidic electrowetting micro-droplet “chip.” The micro-droplets are transported over the planar array of microelectrodes in tightly-controlled fashion by temporally sequencing the electric potential applied to individual microelectrodes. The micro-droplets are moved into areas of thermal contact with portions of a heat-producing integrated circuit dye, housing, packaging, heat-sink, etc., where they absorb heat and then are moved to other areas, volumes, or reservoirs where the absorbed heat can be discharged, for example by means of an active cooling element such as a thermoelectric cooler. In addition to the transport of micro-droplets, those authors describe various means of controlling the surface-area and temporal duration of micro-droplets exposure to heat sources, droplet routing strategies, and other innovations. Also useful experimental data resulting from prototypes are reported, including the fact that larger droplets with longer exposure times to heat sources perform cooling functions better than smaller droplets with shorter exposure times to heat sources.
In the afore-cited text, those authors later describe adapting the microfluidic electrowetting micro-droplet planar microelectrode array and micro-droplet transport to implementations using Printed Circuit Boards (“PCBs”). Two approaches are considered in some detail, these being the “confined system” represented in FIG. 2 and the “open system” represented in FIG. 3. In each of these systems, micro-droplets are moved into areas of thermal contact with portions of a heat-producing integrated circuit dye, housing, packaging, heat-sink, etc., where they absorb heat and then are moved (via sequencing the electric potential applied to the microelectrodes) to other areas, volumes, or reservoirs where the absorbed heat can be discharged. FIGS. 4a and 4b (each adapted from Adaptive Cooling of Integrated Circuits Using Digital Microfluidics by P. Paik, K. Chakrabarty, and V. Pamula, Artech House, 2007, ISBN 978-1-59693-138-1) depict example routing paths of micro-droplets over the planar microelectrode array.
However, in the afore-cited text, those authors limit themselves to planar microelectrode arrays and accordingly planar micro-droplet transport paths. For a micro-droplet exposed to heat in central areas of a microelectrode array and which must then be transported to the edges of the microelectrode array to dispense the absorbed heat, the micro-droplets can unfortunate radiate heat back into other portions of the heat-producing integrated circuits. Those authors allude to methods for minimizing the time over which unintended heat-radiation can occur by heated microdroplets.
Further, the afore-cited text does not provide consideration to avoiding undesired electromagnetic field and electrical field effects that can interfere with adjacent high-performance electronic circuitry.
In addition to these issues and problems, the afore-cited text only considers the cooling of heat-producing integrated circuits. Energy harvesting is not considered.
Accordingly, the reciprocal properties of heat transfer and energy harvesting (via classical Peltier and Seebeck processes) are not considered, nor therefore arrangements to implement adaptive selection between cooling and energy harvesting modalities.
Additionally, the afore-cited text only considers traditional semiconductor thermoelectric elements and does not cite nor anticipate the far higher-efficiency quantum-based thermoelectric materials such as quantum well and Atvo metals. These transform classical Peltier and Seebeck processes to vastly different effects with not only radically improved performance crossing (for the first time) important application-feasibility thresholds but also, in many areas, entirely different engineering and economic tradeoffs.